BOYCOTT : THE RADULA OF HYALINIA. 215 



belonging to the same " family," using the word in the human sense. 

 At any rate, no greater approximation to homogeneity of material 

 could be attained without resource to artificial breeding which, for 

 the present purpose, is clearly undesirable. The other species found 

 at tlie same spot were Hy. cellaria, Hy. 7iitidula, Hy. pura, Helix 

 hispida, Helix rofundata, Cochlicopa lubrica, and C. elegans. The 

 locality is dry, about 460 feet above sea level, on chalk, with an annual 

 rainfall of some 28 inches.^ 



The snails corresponded in every particular, external and internal, 

 with the species described by J. W. Taylor^ as H. helvetica. Speci- 

 mens were submitted to Mr. Taylor, who agreed that they were that 

 species ; Mr. B. B. Woodward also identified specimens as Vitrea 

 rogersH' Whatever the proper name may be, there is, therefore, no 

 doubt as to the sort of snail with which I am dealing. 



The radulae were prepared by soaking and boiling in dilute caustic 

 soda, washing in water, and mounting in Farrant's medium. As far 

 as possible, the same procedure was adopted in every case, so that 

 the results should be as nearly comparable among themselves as could 

 be. I have not been able to make out that such differences in tech- 

 nique as might occur if different people practised what was ostensibly 

 the same method, have any great influence on the form and structure 

 of the radula ; but such might be the case. 



In all, 125 radulae have been examined, from shells varying in size 

 (major diameter) from 3.0 to 8.8 mm., no larger specimens having 

 been obtained. The results are summarised in the following tables, 

 the snails being grouped according to the major diameter. Shell 

 dimensions were measured to o.i mm. on a microscope with a travel- 

 ing stage. As regards the number of whorls, it is simplest to explain 

 the procedure which I adopt, by saying that the helvetica figured by 

 J. W. Taylor on plate vi. of the third volume of his Monograph 

 would be reckoned as having 4I whorls, the lucida 5^ ; that figures 

 8, It, and 14 on plate vi. of the tenth volume of this Journal show 

 Ss' 4'!' 4^ whorls respectively. The method commonly in use would, 

 I believe, attribute about half-a-whorl more in each instance. My 

 procedure is very likely erroneous ; it has, however, been applied 

 consistently. The number of rows — by which I always mean trans- 

 verse rows — requires no comment ; the possibilities of error by reason 

 of the immature rows at the posterior end are familiar to everyone, 

 and are not very material when the comparison between different 

 radulse is made by the same person under similar conditions. With 



1 The Water Supply of Surrey, by W. Whitaker (Geological Survey, 1912), p. 28 and map. 



2 Monograph, vol. iii., p. 45- 



3 Journal of Conch., vol. x., p. 309 ; see also E. W. Bowell, Proc. iMalac. Soc, vol. viii. 

 p. 53. 



